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Патент USA US3093753

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J1me 11, 1963
c. H. BLAKEWOOD ETAL
3,093,735
ENERGY STORAGE DEVICE
Filed Jan. 22, 1960
4 Sheets-‘Sheet 1
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CONDUCTION BAND
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ELECTRON
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TRAPPING
LEVEL
SILVER
THERMALLY
EXCITED'HOLE TRAP
—OPTICALLY EXCITED
LEVEL
HOLE TRAP LEVEL
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VALENCE
ENERGY DIAGRAM
BAND
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22 TRANS
INVENTORS
CHARLES H. BLAKEWOOD
—1:—?- 3
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BY
“Jim
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June 11, 1963
c. H. BLAKEWOOD ETAL
3,093,735
ENERGY STORAGE DEVICE
Filed Jan. 22-, 1960
4 Sheets-Sheet 5
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INVENTORS
. 'BLAKEWOOD
W RSCHA UER
June 11, 1963
3,093,735
C. H. BLAKEWOOD ETAL
ENERGY STORAGE DEVICE
Filed Jan. 22, 1960
4 Sheets-Shqet 4 \
74
78
77'
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76
INVENTORS
CHARLES H. BLAKEWOOD
DOUGLAS M.WARSCHAUER
BYDON
DC. RE NOLDS
L44.
W'“
GEN
United States Patent 0 " ice
3,093,735
Patented June 11, 1963
1
2
band, these electrons can make transitions to the valence
3,093,735
band, thereby emitting green light.
ENERGY STORAGE DEVICE
The next level 14 is the silver level which may or may
Charles H. Blakewood, Baton Rouge, La., Donald C.
Reynolds, Spring?eld, Ohio, and Douglas M. War
not be present in the crystal. Electrons from the silver
schaner, Newton Center, Mass, assignors to the United
States of America as represented by the Secretary of the
level may also make transitions down to holes in the
Air Force
transitions involve an emission of radiation of wave-length
valence band, provided such holes are present.
Such
Filed Jan. 22, 1960, Ser. No. 4,581
7 Claims. (Cl. 250-83)
(Granted under Title 35, US. Code (1952.), see. 266)
of about 6000 angstroms. Other levels, depending upon
the doping agent used, may exist in the crystal.
The invention described herein may be manufactured
and used by or for the United States Government for
governmental purposes without payment to us of any
level 15 and, the optically excited hole trap level 16.
The next two levels are the thermally excited hole trap
These two levels are characteristic of compounds made
up from elements taken from group II and group VI in
royalty thereon.
This invention relates to an energy storage device cap
the periodic table, for example, cadmium sul?de and
cadmium-zinc sul?de compounds in their crystalline form.
15
These levels may yield electrons to the conduction band,
in which case a hole is trapped in this level.
able of storing energy for long periods of time.
One object is to provide an energy storage device where
in energy can be stored by irradiating the device with
light up to 6900 angstroms.
Another object is to provide an energy storage device 20
If a sample crystal, which is normally held at liquid
nitrogen temperature, or about —-150 degrees centigrade,
is warmed to a temperature between carbon dioxide
temperature and room temperature, electrons are excited
wherein the energy may be stored by thermal means.
Another object is to provide a device wherein an in
from the thermally excited level to the conduction band,
leaving holes behind in the thermally excited level. The
electrons in the conduction band contribute to electrical
conduction across the sample if a voltage is applied. This
dication of the stored energy may be produced by me
chanical means.
A further object is to provide a device wherein an
indication of the stored energy may be produced by infra
red irradiation.
'
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conduction remains even after the source of radiation is
removed and the sample is cooled back to the temperature
.
of liquid nitrogen. By mechanical tapping or illumination
A still further object is to provide a device wherein
the indication is in the form. of a change in conductivity.
These and other objects will be more fully understood
with infra-red energy between 9000 and 15,000 angstroms,
the holes from the thermally excited level can be excited
from the following detailed ‘description taken with the
to the valence band so that the electrons in the conduction
drawing wherein:
band, which have been trapped in the electron trapping
FIG. 1 shows an energy diagram for a material such as
used in the device of the invention;
light energy to stimulate the cell and mechanical tapping
level, can make the transition from that level to the
valence band. These transitions involve the emission of
green light ‘and also a decrease in the conductivity of the
sample. The axis along which the crystal is grown will
to release the energy;
hereafter be referred to as the C-axis and‘the release the
FIG. 2 shows a device using a storage cell which uses
'
energy the crystal must be tapped along this
When the sample is illuminated with 6900 angstroms
light, electrons are excited ‘from the optically excited hole’
trapping level to the conduction band from where they
FIG. 3 shows a device similar to the device of FIG. 2
which uses an electro-mechanical transducer to provide
the tapping;
FIG. 4 shows a device similar to FIG. 2 which senses
can make the transition to the valence band as described
previously. The electrons in the electron trapping level
FIG. 5 shows a device similar to FIG. 2 in which infra
and the silver level can not make the transition to the
red illumination is used to release the energy;
FIG. '6 shows a device using a storage cell which uses 45 valence band unless there are holes present in the valence
band. Thus holes trapped at 15 and 16 provide the
thermal energy to stimulate the cell and mechanical tap
the release of energy by the change in conductivity;
ping to release the energy;
‘
storage effect.
.
,
If the sample is doped with silver, electrons from the
FIG. 7 is .a view along the line 7--7 of FIG. 6;
FIG. 8 shows a device similar to FIG. 6 which senses
silver level also make transitions down to holes in the
the release of energy in the form of light in the range
valence band, provided such holes are present, and such
transitions involve the emission of red light of wave
length of about 6000 angstroms. Light of other colors
may be obtained with other doping agents. In FIGS. 2-5,
light with wave lengths shorter than 6900 angstroms such
between green and red in the visible spectrum;
FIG. 9 shows a storage tube fusing the storage device
of the invention;
’
FIG. 10 is a schematic showing of the storage screen
of FIG. 9;
'
55 as ultraviolet light is used to stimulate the crystal and
like elements in these ?gures are given like reference
FIG. 11 shows the ‘device of FIG. 9 modi?ed to use,
thermal energy to stimulate. the storage cells;
FIG. 12 shows one possible storage unit which uses a
?ying spot scanner to illuminate the storage units.
numbers. ‘FIG. 2 has a storage crystal 20 located with
in a container '21 ‘on a block of copper 22. The crystal
is cooled by liquid nitrogen 23. The crystal is stimulated
by irradiating it with light of a wave length of 6900
Referring more particularly to FIG. 1 of the drawing
wherein, reference number 11 refers to the conduction
angstroms or shorter, from a source 24. After the illumi
nation is removed, the crystal is tapped on the side 25
band in the energy diagram and 12 refers to the valence
band. Between these two bands, four bands are shown,
by a mass 26 which is suspended from a support 27.
Movement of the .mass can be due to acceleration or
rectly below the conduction band is the electron trapping 65 other means such as mechanical means or from the action
to, and, from which various transitions are possible. , Di
of an electro-rnagnet. When the mass strikes the side
25, a green light is given off which is sensed by a sens;
level 13. Green light is emitted if an electron from this
level makes a transition to the valence band. The wave
ing unit 28 which may be a photomultiplier.
In.
length of this green light is approximately 5200 angstroms.
an accelerometer, acceleration can be sensed by an out
This level is in equilibrium with the conduction band, 70 put from sensing unit 28 due to the inertia of mass 26
which means that electrons in the conduction‘band may be
trapped in this level and, if holes are present in the valence
causing it to strilre face 25 after the crystal has been
,
stimulated.
_
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3,093,725
4
The mechanical tapping can also be produced by an
9 modi?ed for use with thermal stimulation with like
electromechanical transducer such as a piezo-electric
transducer as shown in FIG. 3. In this device an electro
elements being given like reference numbers. In this
device the electrode 72 is spaced from cooling liquid 73
and connected thereto by means of straps 95. Otherwise
put from sensing unit 23 due to the inertia of mass 26
in FIG. 2. The transducer 29 must be spaced at small
distance from block 20 so as to provide the mechanical
the device is the same as FIG. 9.
‘FIG. 12 shows a plurality of storage cells 99. These
cells are stimulated by light from light source 100 which
is modulated by a light modulating device 101 which
In the device of FIG. 4 use is made in the change in
may be a Kerr cell of electro-mechanical modulator and
conductivity of the sample, when the light is given off
due to the mechanical tapping, to produce an output sig 10 is scanned across the cells by a scanning device 102
which can be a mechanical scanner. The individual out
nal. The output is taken off of electrodes 35 and 36.
puts can be taken off of common lead 103 and individual
It is obvious that the electro-‘mechanical transducer of
leads 104. The information on the cells can be removed
FIG. 3 could also be used with the device of FIG. 4. A
by an infra-red light between 9000 to 15,000 angstroms
few thousand ?ashes have been obtained with these de
from source 105.
vices and the conductivity of the sample changes after
Though cooling means have been shown with all of
each ?ash so that by applying certain predetermined sig
the devices, no cooling means is needed when the device
nals to the electro-mechanical transducer various shapes
is operated in space as radiation from the cell will pro
of output signals can be produced, for example, the con
vide the cooling.
ductivity can be made to change in a step manner by ap
There is thus provided a storage cell capable of storing
plying the signal to the transducer in the form of bursts. 20
energy for long periods of time.
In the device of FIG. 5 infra-red radiation between
While certain speci?c embodiments have been de
9000 and 15,000 angstroms is used to release the energy.
scribed in some detail, it is obvious that numerous
The green light given o?? is sensed by sensing unit 28 as
changes may be made without departing from the general
in FIG. 2. Light other than green may also be obtained
principles and scope of the invention.
by use of the proper doping agents.
We claim:
The devices of FIGS. 6-8 use thermal energy or very
1. An energy storage unit comprising: a crystal of
long wave length infra-red energy applied for a time
cadmium sul?de at the temperature of liquid nitrogen,
suf?cient to heat the crystal to simulate the storage unit.
means for illuminating said crystal with radiation with
In the device of FIG. 6 a storage crystal 40 has two
copper electrodes 41 and 42 located on opposite sides 30 a wave length shorter than 6900 angstroms, to thereby
store energy therein, means for mechanically tapping
thereof. A pool of liquid nitrogen 43 is supplied to cool
said crystal along the C-axis of said crystal to thereby
the crystal. Heat is conducted from the crystal by two
release said energy and means for sensing the release of
heat and electrically conductive support elements 44 and
said energy.
45 and conductive support straps 46 and 47. The straps
2. An energy storage unit comprising: a crystal of
46 and 47 are very thin to permit the crystal to be heated
cadmium sul?de, means for cooling said crystal to liquid
and stimulated by the thermal energy from source 48
nitrogen temperature, means for illuminating said crystal
passing through window 49, as shown in FIG. 7. A mass
with radiation with a wave length shorter than 6900
50 similar to 26 in FIG. 2 and operated in a similar man
angstroms, to thereby store energy therein, means for
ner causes the crystal to give up light energy and change
its conductance. An output is taken off of leads 51 and 40 mechanically tapping said crystal on a side perpendicular
52. An output in the form of green or other colored
to the C-axis of said crystal to thereby release the stored
light, depending upon the doping agent, could also be
energy within said crystal in the form of green light and
used with this device.
means responsive to said green light for producing an out
The device of FIG. 8 is similar to that of FIGS. 6 and
put signal.
7 with like elements being given like reference numbers.
3. An energy storage unit comprising: a crystal of
In the device of this ?gure, infra-red radiation from
cadmium sul?de, means ‘for cooling said crystal to liquid
source 60 illuminates cell 40 to release the energy and
nitrogen temperature, means for illuminating said crystal
the released energy in the form of green light is sensed
with radiation ‘of a Wave length shorter than 6900
by :sensing unit 61 to produce an output at 62. It is
angstroms, to thereby store energy therein, an electro
obvious that the change in conductance could also be
mechanical transducer located on a side of said crystal
used with this device to obtain an output.
perpendicular to the C-axis of said crystal, means for
In the device of FIG. 9 the change in conductive prop
applying a signal to said transducer to thereby release
erties of the crystal are used in a storage tube.
the energy within said crystal and means ‘for sensing the
A cathode ray tube 70 has a screen 71 made up of
release of said energy.
storage elements as shown in FIG. 10 mounted within
4. An energy storage unit comprising: a silver doped
the envelope. The storage elements are located on a
crystal of a mixture of cadmium sul?de and zinc sul?de,
heat and electrical conductive electrode 72 and is cooled
means for cooling said crystal to liquid nitrogen tempera
by liquid nitrogen 73. This screen can be made by secur
ture, means for illuminating said crystal with ultra-violet
ing large crystals to the copper plate with a conducting
light to thereby store energy therein, an electro-rnechani
bonding agent such as silver loaded plastic and then by
60 cal transducer located adjacent one of the sides of said
etching or sand blasting the plate after a mask has been
crystal perpendicular to the C-axis of said crystal, means
placed over the crystals to thereby provide individual
for applying a signal to said transducer to thereby release
crystal of a size depending upon the resolution desired.
the stored energy with said crystal in the form of green
Certain of the cells are stimulated by an image of light
light and means responsive to said green light for pro
with wave lengths shorter than 6900 angstroms focused
ducing an output signal.
upon the screen by a lens 74. The conductivity of the
5. An energy storage unit comprising: a crystal con
elements is sensed by a cathode ray beam from source
sisting of a mixture of cadmium sul?de and Zinc sul?de,
76 which is scanned across the screen by deflection
means for cooling said crystal to liquid nitrogen tem
means 77 and 78 and an output is taken off at 79. The
perature, means for illuminating said crystal with radia
image can be erased either by tapping or by irradiation 70 tion with a wave length shorter than 6900 angstroms, to
thereby store energy therein, an electro-mechanical trans
with infra-red energy between 9000 and 15,000 ang
ducer located adjacent one of the sides of said crystal
stroms from source 80. When the image is erased a
perpendicular to the C-axis of said crystal, means for
light output signal is produced which may also be used
applying a signal to said transducer to thereby release
if desired.
The device of FIG. 11 is similar to the device of FIG. 75 the energy within said crystal and means for sensing the
tapping.
3,093,735
change in conductivity of said crystal when said energy
is released.
6. An energy storage unit comprising: a crystal of
cadmium sul?de, means for cooling said crystal to liquid
nitrogen temperature, means for illuminating said crystal
with radiation with a Wave length shorter than 6900
angstroms, to thereby store energy therein, an electro
mechanical transducer located adjacent one ‘of the sides
of said crystal perpendicular to the C-axis of said crystal,
means for applying a signal to said transducer to thereby 10
release the energy within said crystal and means for
sensing the change in conductivity of said crystal when
said energy is released.
7. An energy storage ‘unit comprising: a cadmium
sul?de crystal having a valence band, a conduction band, 15
a thermally excited hole trapping level and an ‘optically
excited hole trapping level, means for cooling said crystal
6
C-axis of said crystal to thereby release the energy stored
therein and means for sensing the release of said energy.
References Cited in the file of this patent
UNITED STATES PATENTS
2,031,884
2,234,328
2,546,160
2,692,950
2,739,243
2,761,070
2,902,605
2,920,205
2,93 6,373
2,990,473
3,031,574
Gray _______________ __ Feb. 25,
Wolff _______________ __ Mar. 11,
Lengyel ____'_ ________ __ Mar. 27,
Wallace _____________ __ Oct. 26,
Sheldon _____________ __ Mar. 20,
Moos et al. __________ __ Aug. 28,
Wallach _____________ __ Sept. 1,
Choyke ______________ __ Jan. 5,
Welker et al. _________ __ May 10,
Kallmann ___________ __ June 27,
Halsted _____________ __ Apr. 24,
1936
1941
1951
1954
1956
1959
1959
1960
1960
1961
1962
to a temperature of about -—150° centigrade, means
for supplying energy to said crystal to raise electrons
OTHER REFERENCES
from one of said hole trapping levels to said conduction 20
Non-Destructive Sensing an Infrared Stimulable Phos
band to thereby store energy therein, means for mechani
phor, IBM Technical Disclosure Bulletin ‘of December
cally tapping said crystal on a side perpendicular to the
1959, vol. 2, No. 4.
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